The present invention relates to a device for thrust recovery, conceived for linking a turboshaft engine and an aircraft engine strut, so as to ensure transmission of the thrust forces of the turboshaft engine to the structure of the aircraft.
In the text as a whole, the terms xe2x80x9cfrontxe2x80x9d and xe2x80x9crearxe2x80x9d refer to the direction of the airflow in the turboshaft engine, from the front to the rear.
Turboshaft engines ensuring propulsion of aircraft are usually mounted under the wings or inside the tail unit, through the intermediary of an engine strut. The link between the. engine and the strut is ensured by two or three linkage devices designed to transmit to the aircraft structure, through the engine strut, the thrust of the engine. These thrusts comprise vertical loads such as the weight of the engine, axial loads resulting from the thrust produced by the engine, lateral loads due in particular to turbulence produced by the wind, and roll loads or torques resulting from the rotation of the engine. The linkage devices must also absorb the dimensional modifications due to axial and radial expansions and contractions of the engine relative to the engine strut.
Generally, at least one of the linkage devices of the turboshaft engine is dedicated, at least partially, to transmission of the thrust forces. This device, usually situated at the rear of the engine, usually comprises a fitting attached to the engine strut, an articulated control bar on the attachment fitting in its central part, as well as two coupling rods linking the ends of the control bar to a structural element of the turboshaft engine, offset towards the front in relation to the attachment fitting. The two coupling rods are oriented almost along the thrust direction of the turboshaft engine.
In order to ensure transmission of the thrust forces even in the event of rupture of a part, the linkage devices fulfilling this function usually comprise a main linkage structure and a security backup linkage structure. The main linkage structure ensures transmission of thrust in normal operating conditions, that is to say when all the parts of the linkage device are intact. The security linkage structure is then inactive. On the other hand, the security linkage structure ensures transmission of thrust between the engine and the aircraft if there is a failure of one of the parts of the main linkage structure.
Document EP-A-0 564 126 describes a device for thrust recovery comprising a main linkage structure and a safety linkage structure. In conventional manner, the main linkage structure comprises an attachment fitting fixed on the engine strut and two coupling rods for transmission of thrust linked to the attachment fitting by a control bar. The security linkage structure comprises two lateral fork shaped yokes on the attachment fitting, in which the extensions of the pivoting axes are received with play through which the coupling rods are articulated on the ends of the control bar.
This thrust recovery device is usually satisfactory. However, it has the inconvenience of having to transit the thrust force along the same pivoting axes both in normal operational conditions and in the case of rupture of one of the parts.
Document EP-A-0 805 108 also describes a thrust recovery device comprising a main linkage structure and a safety linkage structure. The main linkage structure is of the same type as that used in document EP-A-0 564 126. The safety linkage structure comprises a supplementary pivoting axis interposed between the attachment fitting and the control bar, crossing the latter with a predetermined play.
This thrust recovery device has the main inconvenience of becoming non-operational when there is breakage of the control bar. In these conditions, the device no longer ensures recovery of the thrust forces and there is a great risk of losing the engine.
Document EP-A-0 879 759 also describes a thrust recovery device comprising a main linkage structure and a safety linkage structure. The main linkage structure is of the same type as that used in the preceding documents. The safety linkage structure comprises pins formed on the ends of the coupling rods articulated on the control bar. These pins enter with play into longitudinal grooves formed in the lugs integral with the attachment fitting.
This device needs to be dimensioned in order to transmit the thrusts correctly. This results in higher weight in relation to the thrust recovery device described in the preceding document.
The objective of the invention is a device for thrust recovery designed to ensure the link between a turboshaft engine and an engine strut of an aircraft, this device being fitted in such a way that it has reduced mass and dimensions and ensures the transmission of the thrust force even in the event of rupture of any one of the parts constituting it.
According to the invention this result is obtained by means of a thrust recovery device, capable of linking a turboshaft engine and an engine strut of an aircraft, the device comprising:
an attachment fitting able to be fixed to the engine strut, said attachment fitting comprising a central yoke and two lateral yokes;
a control bar containing a central part articulated on the central yoke of the attachment fitting by a first pivoting axis; and
two coupling rods oriented almost along the direction of the turboshaft engine thrust and each comprising a front end able to be articulated on the turboshaft engine and a rear yoke, articulated by a second pivoting axis on a lateral extremity corresponding to the control bar;
said device being characterised in that the rear yoke of each of the coupling rods is also articulated on one of the lateral yokes of the attachment fitting, by a link with play comprising a third pivoting axis.
In this device, the security linkage structure comprises pivoting axes distinct from those which are used by the main linkage structure. In addition, the thrust force recovery is ensured even in the hypothesis of rupture of the control bar, wherever the zone of this rupture is located.
According to a preferred embodiment, the second and third pivoting axes intersect the longitudinal axis the corresponding coupling rod.
Preferably, the lateral yokes of the attachment fittings are male yokes and the rear yokes of the coupling rods are female yokes.
Advantageously, the lateral ends of the control bar the n enter the female yokes of the coupling rods, in front of the lateral yokes of the attachment fittings.
Preferably, the first, second and third pivoting axes are parallel to each other.
In the preferred embodiment of the invention, the central yoke of the attachment fitting is also a female yoke receiving the central part of the control bar.